In semiconductor devices such as DRAMs (Dynamic Random Access Memory), element isolation regions are provided in the surface of a silicon substrate using STI (shallow trench isolation), and these demarcate a plurality of active regions in a matrix formation. The element isolation regions include first element isolation regions which isolate the active regions in a bit line direction, and second element isolation regions which isolate the active regions in a word line direction. Patent literature article 1 discloses examples of such element isolation regions and active regions.